The cultivated tomato, Solanum lycopersicum L., a fruit that is often treated as a vegetable, is widely grown around the world and constitutes a major agricultural industry. Worldwide, it is the second most consumed vegetable after potato (FAOSTAT 2005) and unquestionably the most popular garden crop. In the U.S., it is the third most economically important vegetable (with a total farm value of $2.062 billion) following potato ($2.564 B) and lettuce ($2.064 B) (USDA 2005; worldwide web at www.usda.gov/nass/pubs/agr05/agstats2005.pdf. In addition to tomatoes that are eaten directly as raw vegetable or added to other food items, a variety of processed products such as paste, whole peeled tomatoes, diced products, and various forms of juice, sauces and soups have gained significant acceptance. There are more varieties of tomato sold worldwide than any other vegetable. Although a tropical plant, tomato is grown in almost every corner of the world from the tropics to within a few degrees of the Arctic Circle. It is grown in greenhouses where outdoor production in restricted due to cool temperatures. Major tomato producing countries in descending orders include China, USA, India, Turkey, Egypt and Italy (worldwide web at faostat.fao.org). Other leading countries include Spain, Brazil, Iran, Mexico, Greece and Russia. In North America, production occurs in the U.S., Canada and Mexico, comprising a total of 310,000 ha. In 2004, the total harvested area in the U.S. was estimated to be 170,808 ha (50,560 ha fresh market and 120,248 ha processing tomatoes) with a total farm value of ˜$2.06 B ($1.34 B fresh market and $0.72 B processing) (USDA 2005; worldwide web at nass.usda,gov:8080/OuickStats/index2.jsp). California and Florida are by far the leading producers of processing and fresh market tomatoes, respectively (USDA 2005). Worldwide, tomatoes are an important part of a diverse and balanced diet (Willcox et al. 2003). By virtue of volume consumed, tomato and tomato products contribute significantly to the dietary intake of vitamins A and C as well as essential minerals and other nutrients. In the U.S. diet, for example, tomato ranks first among all fruits and vegetables as a source of vitamins and minerals (Rick 1980) and phenolic antioxidants (Vinson et al. 1998). Also, fresh and processed tomatoes are the richest sources of the anti-oxidant lycopene (Nguyen and Schwartz 1999), which can protect cells from oxidants that have been linked to cancer (Giovannucci 1999) (see below).
In addition to the appearance and taste, consumers' perceptions of fruit quality are now influenced by perceived health benefits. Fruit color is a quality characteristic that has received intensive attention by fresh-market and processing tomato industries as well as consumers. The final color in tomato fruit is conditioned by the total amount and proportion of different carotenoids. Lycopene is the red pigment and a major carotenoid in tomato. In processing tomato, fruit color influences the grades and standards of the processed commodity. In fresh market tomato, fruit color has significant effect on its marketability. The attention to fruit color has recently been on the rise due to the increasing knowledge of the health benefits of different carotenoids. Fresh tomatoes and tomato products are presently major sources of LYC, a potent natural antioxidant that is increasing in demand. Numerous epidemiological and intervention studies have demonstrated that dietary intake of LYC-rich foods results in decreased incidence of certain cancers, including the prostate, lung, mouth, and colon cancers, and the coronary heart diseases, cataracts and may be macular degeneration (Gerster 1997; Giovannucci 1999; Giovannucci and Clinton 1998; Sies and Stahl 1998; Tsubono et al. 1999; Willcox et al. 2003). This attention to lycopene is well deserved, as its antioxidant capacity is roughly twice that of β-carotene (Di Mascio et al. 1990). As the scientific community has become more aware of the impact of carotenoids on human health, attention has shifted to increasing tomato fruit lycopene content.
Although tomato is the richest source of lycopene among all fruits and vegetables, its concentration in the fruit of commercial cultivars is rather low, on average ranging from 30 to 60 Jig lycopene/g fresh tomato tissue. An increase in the concentration of lycopene in commercial cultivars of tomatoes has been an interest of plant breeders, growers and processors. Previously, spontaneous mutations contributing to high lycopene content were identified in S. lycopersicum, including two recessive mutant genes, hp1 (high pigment 1) (Yen et al. 1997) and hp2 (van Tuinen et al. 1997) which were mapped to tomato chromosomes 2 and 1, respectively. The hp genes increase the total fruit carotenoids, including β-carotene (Palmieri et al. 1978). These genes were subsequently introgressed into several tomato cultivars (Soressi 1975; Thompson et al. 1962). However, the adverse pleiotropic effects of hp genes, such as slow germination and seedling growth, seedling mortality, inferior leaf coverage, brittle stems, low yield, reduced total acidity and soluble solids content (SSC), high sensitivity to various pathogens and premature defoliation, have prohibited widespread commercial use of these genes (Wann 1995). Efforts to reduce these negative effects have largely failed and thus, currently only a handful of lycopene-rich tomato cultivars carrying hp1 or hp2 are being used in intensive production. Furthermore, as both of these genes are recessive in nature, they are undesirable for production of hybrid cultivars with high fruit lycopene content. Additional neutral pleiotropic effects of these genes include accumulation of anthocyanin in hypocotyls, shorter and darker hypocotel, and dark green immature fruit.
In addition to hp1 or hp2, a crimson gene (ogc, cr) has been identified and mapped to tomato chromosome 6 which increases fruit lycopene content of the cultivated tomato by about 25%, though at the expense of β-carotene (Ronen et al. 2000; Thompson et al. 1967). This gene has been incorporated into many recent tomato breeding lines and cultivars, and commercial hybrids containing this gene are available. The ogc is physically tightly linked to a self-pruning gene (sp) gene on chromosome 6, and thus high lycopene plants (homozygous for ogc) are all determinate in nature. There has been no report of an indeterminate plant (sp+sp+) with high lycopene content (i.e. with ogc gene). This is a major limitation of this technology.
It is an objective of the present invention to disclose a novel Solanum pimpinellifolium accession designated as LA2093 previously designated LAxxxx or PSPL125 that can be used as a source of high fruit lycopene content. The fruit lycopene concentration of this accession is as high as 390 μg/g fresh tomato tissue. It is a further objective of this invention to provide Solanum lycopersicum plants which are high in fruit lycopene content, in the range of 100-200 μg/g fresh tomato tissue.
It is yet another object of the invention to provide genetic markers which may be used for marker assisted selection to incorporate the high lycopene content trait into tomato plants and other Solanum species.